Electrolytes for the electrolytic deposition of zinc

ABSTRACT

An aqueous alkaline zinc bath is used for electroplating bright metallic zinc deposits on metal substrates said plating bath containing less than about 2 oz./gal. of cyanide therein, and comprising an aqueous alkaline solution having dissolved therein a soluble zinc compound capable of being plated by electrolytic deposition and a water soluble reaction product of an amine and an epihalohydrin containing recurring tertiary and/or quaternary amine groups and having a molecular weight above about 250 in an amount from at least about 0.1 gm./liter.

llnite States Patent Nobel et a1; 1451 Mar. 4, 1975 1 ELECTROLYTES FOR THE 2,791,554 5/1957 Wint,ers.... 204/55 Y ELECTROLYTIC DEPOSITION 0 C 1/1966 Burnson r. 204/55 Y [75] Inventors: Fred 1. Nobel; Barnet D. Ostrow,

both of Roslyn, N.Y. [73] Assignee: Lea-Rona], Inc., Freeport, NY.

[22] Filed: Nov. 5, 1973 [21] Appl. No.: 412,817

Related U.S. Application Data 163] Continuation of Ser. No. 268,920, July 3, 1972, abandoned, which is a continuation-in-part of Ser. No, 17,302, March 6, 1970, abandoned, which is a continuation-in-part of Ser. No. 640,339, May 22. 1967, abandoned.

152] U.S. C1. 204/55 Y, 204/D1G. 2, 204/55 R [51] Int. Cl ..C23b/5/10, C23b 5/46 [58] Field of Search ..204/55 R,,55 Y, 43 Z44, 204/114; 106/1 [5 6 References Cited UNITED STATES PATENTS 2,451.426 10/1948 Bair et a1. 204/55 Y 5/1967 Dahlmann 204/55 R Primary Examiner-G. L. Kaplan Attorney, Agent, or Firm-Pennie & Edmonds 1 1 ABSTRACT An aqueous alkaline zinc bath is used for electroplating bright metallic zinc deposits on metal substrates molecular weight above about 250-in an amount from at least about 0.1 gm./liter.

10 Claims, No Drawings ELECTROLYTES FOR THE ELECTROLYTIC DEPOSITION OF ZINC CROSS REFERENCE TO RELATED APPLICATIONS BACKGROUND OF THE INVENTION The field of this invention relates to electrolyte solutions or baths useful for the electrolytic deposition of metallic zinc on various substrates well known in the art of the electrolytic deposition of zinc.

The major portion of zinc plating is done today from alkaline solutions containing a soluble zinc compound and substantial quantities of sodium cyanide. This sodium cyanide solution plates zinc that is semi-bright, and in order to obtain bright zinc deposits, a large variety of brighteners are added to the plating solutions. These brighteners are well known in the art and include a wide variety of compounds, such as aldehydes, ketones, thiourea, organic acid salts, and so forth.

These cyanide-containing baths are obviously objectionable due to the poisonous nature of the cyanides and present serious problems of disposal, particularly since waste disposal has become and important national problem in this country and elsewhere.

As a result of thewaste disposal problem with the cyanide baths, much effort has been put into development of cyanide-free electrolytes which will eliminate this serious waste disposal problem. i I

Some cyanide-free or substantially cyanide-free zin plating baths are in existence today, and most of these baths appear to be based on a solution of sodium zincate with excess sodium hydroxide. High pH alkali zincate baths when used without brightening or addition agents yield deposits that are dull, spongy and of poor appearance. It has been proposed to overcome these deficiencies by adding glycolates to increase smoothness of dep osits but commercially acceptable bright plates were not obtainable. ,It has also been proposed rate in the high pH zincate baths alkylene amines such as ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine, either alone or in conjunction with an aldehyde compound. The latter baths although producing bright deposits and being.

comparatively more stable than previous baths, nevertheless has the serious short-coming of a very narrow bright plating range as well as poor throwing power. These factors made such baths commercially unacceptable according to todays requirements.

In most cases, production experience has indicated that even these so-called cyanide-free solutions or baths require small quantities-of sodium cyanide-to make them commercially operative, particularly with respect to bright deposits according to todays requirements.

Epichlorohydrin-amine reaction products have previously been disclosed as being useful in aqueous zinc cyanide electroplating baths, but not to applicants knowledge in cyanide free or substantially cyanide free zinc plating baths. The Winters U.S. Pat. No. 2,79l,554,-for example, discloses the use of epichlorohydrin reaction products with ammonia or primary amines inconventional zinc cyanide baths using 10 to 12 ounces/gallon of zinc cyanide. Although epichlorohydrin-primary amine reaction products, containing recurring primary amine groups, have been used in zinc cyanide baths, they arenot good enough to meet todays standards for non-cyanide or low cyanide zinc baths with respect to throwing power, current density and brightness and of course cannot aid in solving the pollution problems because of the presence of the cyanide. In addition, the ethylene diamineepichlorohydrin reaction product produced according to the Example beginning at line 68, column 2 of the Winters patent substituting ethylene diamine for the ammonia in the amount specified at lines 4955, column 3 was prepared and analyzed for amine content according to the well-known method published in Quantitative Organic Analysis via Functional Groups by Dr. Sidney Siggia, J. Wiley & So'ns Inc. 3rd Edition, page 450,

Determination of Amines in Mixtures: Primary, Sec-' ondary and Tertiary Amines via Schiff Base and Acetylation Approach (Siggia, Hanna, Kervenski. Anal Chem. 22 page l295 in 1950). The results showed that the Winters product contained 13.7 percent primary amine groups, 14.2 percent secondary amine groups, less than 0.5 percent tertiary amine groups, and no quaternary amine group. The figure 0.5 percent for the tertiary amine groups is within experimental error and thus the product can be said to contain no tertiary aminegroups for all practical purposes and certainly the tertiary amine groups, if any, are not recurring" as required according to this invention.

The Burnson U.S. Pat; No. 3,227,638 discloses the use ofa cyclic amine, namely, hexamethylenetetramine' reacted with epichlorohydrin, again in'cyanide electroplating baths. The use of this reaction product in conventional zinc cyanide baths, low cyanide baths (about 2 oz./gal.) or even in cyanide-free baths results in insufficient or poor stability of the bath which is unacceptable to meet todays standards. In addition, the use of large amounts of secondary brighteners are used in low cyanide baths to obtain an acceptable brightness;

SUMMARY OF THE INVENTION i The present invention provides a zinc plating bath which can be'completely devoid of cyanide and which is capable of being used in the electrolytic deposition of zinc having a brightness and throwing power close to or better than that which can be obtained from commercial cyanide zinc plating baths'Broadly stated, the plating bath of this invention contains an alkaline soluble zinc compound and a water soluble polyelectrolyte which is the reaction product of an epihalohydrin and an alkylene amine resulting in a'plating bath having expower to meet the requirements demanded by the plating industry today.

DESCRIPTION oF THE PREFERRED EMBODIMENTS The alkaline soluble zinc salts which can be used in the plating baths according to this invention can be of any zinc compound soluble in an alkaline medium caples of such zinc compounds andsalts are well known in the art and include, for example, zinc sulfate, zinc acetate, and zinc oxide. Other alkaline soluble zinc compounds can of course be used, as will be apparent to those skilled in the art.

The amount of zinc metal in the bath is not critical and can be varied, as known in the art, with respect to other known zinc plating baths. Preferably, however, the zinc metal content of the baths of this invention is between about 1 to 4 ounces per gallon.

The zinc metal content can be supplied to the bath by means of a conventional soluble zinc anode orby the use of an insoluble anode and by direct addition of the appropriate alkaline soluble zinc compound'fto the plating solution.

The alkalinity can be supplied to the aqueous baths by any alkaline material so long as it is capable of dissolving the zinc compound used in the aqueous bath to ide and potassium hydroxide can be used to supply the alkalinity. Sodium hydroxide is preferable, however, since sodium hydroxide has better solubility with respect to alkali zincates.

The amount of alkaline compound, such as sodium hydroxide, should advantageously be in excess of that required to form the sodium zincate. The amount of excess of free sodium hydroxide is not critical, so long as it is sufficient to keep all the zinc in solution and prevent any precipitation of the zinc from taking place.

The pH of the electrolyte solutions according to this invention can of course be varied to obtain optimum results as will be apparent to those skilled in the art. The pH of the electrolyte solutions of this invention are, however, advantageously maintained at 12 and above.

Thepolyele'ctrolytes useful asadditives according to this invention for producing bright zinc platings from cyanide-free or substantially cyanide-free electrolytes are water-soluble polycondensates, of an alkylene amine, and an epihalohydrin. The polycondensates are in the form of a polymer containing repeating tertiary and/or quaternary amine groups and have a molecular weight above about 250 but below that which would render the polycondensates water insoluble or insoluble in the electrolyte solution. Advantageously the condensates have a molecular weight above 1000. Polyelectrolytes with molecular weight in the range between 4,000 and 5,000 are particularly advantageous.

Polymeric. amines reacted with compounds having functional groups capable of reacting with the amine may also be used as additives according to this invention provided that the polymeric products contain re- .curring tertiary or quaternary amine units and have a pable of beingplated by electrolytic deposition. Examthe desired extent. For example, both sodium hydroxcurring tertiary and/or quaternary amine groups, such as by a conventional quaternization reaction as set forth in Procedure ll below.

Polycondensat es containing recurring primary and- /or secondary amine groups do not produce the advantageous results of this invention when used in noncyanide or low cyanide zinc plating baths as are obtained by the use of the polycondensates containing recurring tertiary and/or quaternary amine groups and therefore do not meet the zinc plating standards of wide current density ranges, brightness, throwing power, etc. desired by the plating industry today.

The presence of some primary and/or secondary amine groups in the polycondensates used according to this invention is permissible so long as there are a sufficient number of recurring tertiary and/or quaternary amine groups present in the polycondensate to accomplish the objects of this invention. The number or amount of primary or secondary amine groups permissible in the polycondensates will depend upon the particular amine used to form the polycondensate as well as other variables and can be determined by routine experimentation by one skilled in the art. The presence of secondary amine groups are more easily tolerated in the polycondensates than primary amines.

Lower alkyl amines are advantageous for'reaction with the epihalohydrin and some examples of amines that can be used according to this invention include trimethyl amine, triethanolamine, dimethyl amino propylamine, diethyl amino propylamine, n-n dimethyl amine ethylamine, n-n' dimethyl n methyl propylene diamine, and'so forth. For example, the methyl, ethyl and propyl groupscan be interchanged in various manners in the above mentioned amines.

Although the polycondensates containing recurring tertiary amines are quite advantageous when used in cyanide free or low cyanide zincate baths, the polyconamines after reaction with the epihalohydrin by. a promolecular weight in excess of 250, preferably above The water soluble epihalohydrin alkylene amine alkyl amines and subsequently reacted to form the re; v

cess such as set forth in Procedure ll below.

The polycondensates of this invention containing repeating tertiary or quaternary amine groups can be prepared using primary amines or mono amines in the initial reaction with an epihalohydrin and the resulting polymer further reacted to form the recurring tertiary 'and/orquaternary amine groups such as by subjecting the polymer to a quaternization reaction as set forth in Procedure II below. Thus the products of the Winterspatent as described above, could be converted into polymers containing recurring tertiary and/or quaternary groups by subjecting the polymers to quaternization with methyl chloride as set forth in Procedure ll below, and thus be rendered useful-according to this invention.

The epihalohydrins that can be used accordingto this invention. include not only the well known Fitisii but various homologs, isomers, saturated or unsaturated so long as they are capable of reaction with an alkylamine, alkyl polyamine or polymerized amines to produce a water soluble product containing recurring and/or quaternary amine groups. Depending on the amine used, and other reaction conditions, the resulting product may have to be quaternerized, for example, by a process similar to that set forth in Procedure [I below to insure the presence of recurring tertiary and- /or quaternary amine groups. A polymer produced according to the procedure is set forth below in Example 1V.

PROCEDURE I One hundred and two grams of dimethylaminopropylamine are added to a three-necked round flask containing 612 grams of water. The flask ,is placed in a water bath and is equipped with an agitator, a thermometer and afunnel with stopcock. After the solution is cooled to and maintained at 25C., 161 grams of epichlorohydrin are added to the aqueous solution in the flask slowly over a period of an hour. The molar ratio of the epichlorohydrin to the dimethylaminopropylamine is 1.75:1. The reaction is allowed to proceed for an additional 30 minutes after all the epichlorohydrin is added to the aqueous solution and thereafter, the reaction product is acidified to a pH of about 6 with sulfuric acid.

PROCEDURE 11 Four hundred and fifty-twograms of dimethylaminopropylamine in 820 ml. of water is reacted with 368 of sodium hydroxide, and is heated therein to C.

under agitation. 300 grams of methyl chloride under a pressure in the range of'2.8 to 3.5 kg/Cm is then used to flush the autoclave and thereafter the autoclave is cooled and the contents are emptied. The resultant solution is adjusted to a solid content of 50 percent and a pH of about 6.

The amount of polyelectrolytes which can most advantageously be used according to this invention will of course vary to some extent depending upon the particular polyelectroly te selected for use-and the brightness of the zinc plating desired. When a basic solution containing sodium zincate'and free sodium hydroxide is used, the deposit is a matte gray color with no luster at all. As small quantities of the polyelectrolyte are added, the deposit becomes semi-bright, and as additional pol yelectrolyte is added, brighter plating will'be obtained until maximum brightness is obtained. Additional amounts of the polyelectrolyte could of course be used if desired. Generally, the addition of 0.1 gram per liter of an epichlorohydrindimethylaminopropylamine condensation product in a sodium zincate bath containing free sodium hydroxide will change the zinc plating from a matte gray color with no luster at all to a semi-bright plating; and as additional amounts of this polyelectrolyte are added, brighter deposits will be obtained. Optimum results have been obtained with about 1.2 to

1.5 grams per liter with the specific polyelectrolyte noted above.

We have also discovered that brilliant deposits that are leveled can be produced with: a plating bath of this, invention in which there is dissolved, in addition to the polyelectrolyte, a conventional aldehyde brightening agent. The combined brightening and leveling effects by the synergistic action of the two additives is not expected because aldehyde brightening agents in zinc cyanide orother zinc baths do not exhibit leveling effects. We further noticed that the amountof aldehyde that is required to give increased brightness is less than that required in the prior zinc baths.

Suitable aldehyde brighteners include vanillin, hydroxybenzaldehyde, anisic aldehyde, bisulfite com pounds of aldehydes, and so forth. The polyelectrolytes of this invention arethe primary brighteners and are required in every case to give good results. The secondary brighteners mentioned above are thus optional for obtaining even brighter zinc plates if desired. The amount of such secondary brighteners, such as anisic aldehyde, can be varied quite widely, as will be apparent to those skilled in the art. For example, anisic aldehyde can be used in combination with the polyelectrolytes in an amount as low as 0.1 grams per liter and up to one gram per liter and even more. Other secondary brighteners useful in noncyanide or low cyanide zinc baths can also be used alone or preferably in combination with the secondary aldehyde brighteners.

A small amount of cyanide, such as sodium cyanide, can be used in the plating solutions of this invention is desired. However, the advantageous results of this invention are not obtained if the amount of cyanide exceeds about 2 oz./gal. The presence of cyanide is, however, not essential for the production of bright zinc plate in accordance with the present invention.

The baths can be operated at conventional amperages for zinc plating baths. For example, anywhere from 0 to 50 amps per square foot as determined by the Hull-Cell evaluation can be used. It is advantageous, however, to utilize between about 25 to 50 amps per square foot, and 25 ampspersquare foot is generelly recommendedfor production plating.

Various articles can of course be plated according to this invention, as is well knownin the art. The zinc plating takes place on the cathode, and the majority of zinc plating is done in steel articles inserted into the baths as cathodes.

EXAMPLE I 2 ozJgal. l6 ozJgal.

EXAMPLE u Zinc metal as Zinc Oxide Sodium Hydroxide Ouaternized condensation reaction product of Epichlorohydrin Dimethylaminopropylamine (Prepared according to Procedure II and having a molecular weight in the range between 4000-5000) Vanillin 3 oz./gal. 32 oz./gal.

' EXAMPLE lIl Zinc metal as Zinc Acetate Potassium Hydroxide Condensation reaction product of Epichlorohydrin Dimethylaminopropylamine (Prepared according to Procedure I] and having a molecular weight in the range between 4000-5000) Anisic Aldehyde (as the bisulfate) 1.5 oz./gal. 25 oz./gal.

All of the above baths were operated utilizing a steel cathode at 25 amps per square foot, and bright zinc deposits were obtained in all instances.

In the above bath operated utilizing a steel cathode at 25 amps persquare foot, a plate of uniform brightness was obtained.

We claim:

1.-An aqueous alkaline zincate bath suitable for depositing bright metallic zinc deposits, and containing less than about 2 oz./gal. of cyanide therein, said bath comprising an aqueous alkaline solution having dissolved therein: I r

a. a soluble zinc compound capable of being plated by electroytic deposition; and Y b.-at least about 0.1 gm./l of a water soluble polyme containing repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) polymerizing an aliphatic amine with an epihalohydrin, said polymerization being carried out for a sufficient length of time, and said reactants being present in such a molar ratio, so as to produce a polycondensate having repeating tertiary and/or quaternary amine groups ahd having a molecular weight above about 250 but below that 8 which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath. 2. The aqueous alkaline zincate bath of claim 1 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.

3. The aqueous alkaline zinc bath of claim 1 in which the soluble polymer containing repeating tertiary amine groups is reacted with a sufficient amount of a quaternizing agent to convert amine groups to repeating quaternary amine groups. I

4. An aqueous alkaline zincate bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal of cyanide therein, said bath comprising an aqueous alkaline solution having dissolved therein:

a. a soluble zinc compound capable of being plated by electrolytic deposition; and

b. at least about 0.1 gm./l of awater soluble polymer containing repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) polymerizing an aliphatic amine com taining a primary amine group with an epihalohydrin, said polymerization being carried out for a sufficient length of time, and said reactants being present in such a molar ratio, so as to produce a'polycondensate having repeating secondary amine groups and having a molecular weight above about 250 but below that which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath, and .(ii) reacting said polycondensate with a sufficient amount of a quaternizing agent to con vert repeating secondary amine groups into repeating tertiary and/or quaternary amine groups. 5. The aqueous alkaline zincate bath of claim 4 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.

6. An' aqueous alkaline zincate bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal. of cyanide therein, said bath comprising an aqueous alkaline solution having dissolved therein:

a. a soluble zinc compound capable of being plated by electrolytic deposition; and

b. at least about 0.1 gm/l of a water soluble polymer containing repeating tertiary and/or quaternary amine groups,.said polymers'having been prepared by (i) reacting and aliphatic amine containing a secondary or tertiary amine group with a polyepihalohydrin, said reaction being carried out for a sufficient length of time and said reactants being present in such a molar ratio, so as to produce a polycondensate having repeating tertiary and/or quaternary amine groups and havinga mo lecular weight above about 250 but below that which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath.

7. The aqueous alkaline zincate bathof claim 6 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.

8. The aqueous alkaline zinc bath of claim 6 in which the soluble polymer containing repeating tertiary amine groups is reacted with a sufficient amount of a quaternizing agent to convert amine groups to repeat ing quaternary amine groups.

- 9 9. An aqueous alkaline zincte bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal. of cyanide therein, said bath commprising an aqueous alkaline solution having dissolved therein:

a. a soluble zinc compound capable of being plated by electrolytic deposition; and b. at least about 0.1 gm./] of water soluble polymer comprising repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) reacting an aliphatic amine containing a primary amine group with a polyepihalohydrin, said reaction being carried out for a sufficient length of time and said reactants being present in such a molar ratio, so as to produce a reaction product wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.-

Q Q UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT N0. 3,869,358

DATED 1 March 4, 1975 INVENTOR(S) Fred I. Nobel et al.

it IS certified that error appears in the ab0ve-identified patent and that said Letters Patent are hereby corrected as shown below:

a Column 1, line 30 "become and" should read become an--.

Column 6, line 55, "done in steel" should read done on steel.

Column 7, line 43 N(CH should read N(CH a Column 7, line 66 "groups ahd" should read groups and--.

Column 9, line 1 "zincte bath" should read zincate bath--.

Column 9, line 4 "comprising" should read comprising-.

Signed and Emalcd this Twenty-seventh Day of J l 1976 Arrest:

RUTH C. MASON C. MARSHALL DANN 411681171X ff Commissioner oj'larenrs and Trademarks E .i i 

1. AN AQUEOUS ALKALINE ZINCATE BATH SUITABLE FOR DEPOSTING BRIGHT METALLIC ZINC DEPOSITS AND CONTAINING LESS THAN ABOUT 2 OZ./GAL. OF CYANIDE THEREIN, SAID BATH COMPRISING AN AQUEOUS ALKALINE SOLUTION HAVING DISSOLVED THEREIN: A. A SOLUBLE ZINC COMPOUND CAPBLE OF BEING PLATED BY ELECTROYTIC DEPOSITION, AND B. AT LEAST ABOUT 0.1 GM./L OF A WATER SOLUBLE POLYMER CONTAINING REPEATING TETIARY AND/OR QUATERNARY AMINE GROUPS, SAID POLYMERS HAVING BEEN PREPARED BY (I) POLYMERIZING AN ALIPHATIC AMINE WITH AN EPIHALOHYDRIN, SAID POLYMERIZATION BEING CARRIED OUT FOR A SUFFICIENT LENGTH OF TIME, AND SAID REACTANTS BEING PRESENT IN SUCH A MOLAR RATIO, SO AS TO PRODUCE A POLYCONDENSATE HAVING REPEATING TERTIARY AND/OR QUATERNARY AMINE GROUPS AND HAVING A 5 MOLECULAR WEIGHT ABOVE ABOUT 250 BUT BELOW THAT WHICH WOULD RENDER THE POLYCONDENSATE WATER INSOLUBLE OR INSOLUBLE IN THE ALKALINE ZINCATE BATH.
 2. The aqueous alkaline zincate bath of claim 1 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.
 3. The aqueous alkaline zinc bath of claim 1 in which the soluble polymer containing repeating tertiary amine groups is reacted with a sufficient amount of a quaternizing agent to convert amine grOups to repeating quaternary amine groups.
 4. An aqueous alkaline zincate bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal of cyanide therein, said bath comprising an aqueous alkaline solution having dissolved therein: a. a soluble zinc compound capable of being plated by electrolytic deposition; and b. at least about 0.1 gm./l of a water soluble polymer containing repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) polymerizing an aliphatic amine comtaining a primary amine group with an epihalohydrin, said polymerization being carried out for a sufficient length of time, and said reactants being present in such a molar ratio, so as to produce a polycondensate having repeating secondary amine groups and having a molecular weight above about 250 but below that which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath, and (ii) reacting said polycondensate with a sufficient amount of a quaternizing agent to convert repeating secondary amine groups into repeating tertiary and/or quaternary amine groups.
 5. The aqueous alkaline zincate bath of claim 4 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.
 6. An aqueous alkaline zincate bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal. of cyanide therein, said bath comprising an aqueous alkaline solution having dissolved therein: a. a soluble zinc compound capable of being plated by electrolytic deposition; and b. at least about 0.1 gm/l of a water soluble polymer containing repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) reacting and aliphatic amine containing a secondary or tertiary amine group with a polyepihalohydrin, said reaction being carried out for a sufficient length of time and said reactants being present in such a molar ratio, so as to produce a polycondensate having repeating tertiary and/or quaternary amine groups and having a molecular weight above about 250 but below that which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath.
 7. The aqueous alkaline zincate bath of claim 6 wherein a secondary aldehyde brightener is dissolved therein in a sufficient amount to increase the brightness of the deposit.
 8. The aqueous alkaline zinc bath of claim 6 in which the soluble polymer containing repeating tertiary amine groups is reacted with a sufficient amount of a quaternizing agent to convert amine groups to repeating quaternary amine groups.
 9. An aqueous alkaline zincte bath suitable for depositing bright metallic zinc deposits and containing less than about 2 oz./gal. of cyanide therein, said bath commprising an aqueous alkaline solution having dissolved therein: a. a soluble zinc compound capable of being plated by electrolytic deposition; and b. at least about 0.1 gm./l of water soluble polymer comprising repeating tertiary and/or quaternary amine groups, said polymers having been prepared by (i) reacting an aliphatic amine containing a primary amine group with a polyepihalohydrin, said reaction being carried out for a sufficient length of time and said reactants being present in such a molar ratio, so as to produce a reaction product having repeating secondary amine groups and having a molecular weight above about 250 but below that which would render the polycondensate water insoluble or insoluble in the alkaline zincate bath and (ii) reacting the reaction product of the polyepihalohydrin containing the secondary amine groups with a sufficient amount of a quaternizing agent to convert repeating secondary amine groups into repeating tertiary and/or quaternary amine groups.
 10. The aqueous alkaline zincate bath of claim 9 wherein a secondary aldehyde brightener Is dissolved therein in a sufficient amount to increase the brightness of the deposit. 